The present invention relates to an annular sustained release pheromone-dispenser which can release a synthetic sex pheromone in the air to control the harmful insects by disturbing the copulative communication of the insects as well as a method for preparing the pheromone-dispenser and a tool for installing the pheromone-dispenser.
The control of a harmful insect through disturbance of the copulative communication thereof is carried out by releasing the synthetic sex pheromone of the insect to be controlled in the air to thus reduce the rate of copulation through the disturbance of their copulative communication and to thereby inhibit the breeding of the next generation. Therefore, a pheromone-dispenser for releasing a synthetic sex pheromone should satisfy such a requirement that it can stably release the sex pheromone over the entire term (2 to 6 months) of the occurrence of the corresponding harmful insect.
The pheromone-dispensers which have already been put on the market are designed in such a manner that a liquid synthetic sex pheromone is enclosed in, for instance, a tube type, bag type, bottle type or spiral tube type plastic container and the sex pheromone which diffuses and permeates through the wall of the container is evaporated and released into the air. Among these pheromone-dispensers, those generally referred to as the tube type ones employ a plastic tubular container (slender tube) and show the most excellent control effect as compared with the other type ones since they can release the sex pheromone vapor over a long period of time and can ensure a uniform release rate.
When using such pheromone-dispensers, they must be set up and distributed so as to uniformly release the synthetic sex pheromone in the field and must stably hold their set up condition over a long time period without imparting any harmful effect and/or damage to the growth of plants.
As conventional tubular type pheromone-dispensers which can satisfy these requirements, Japanese Patent Application Publication Nos. 61-16361 and 2-63017 disclose those in which a metal wire such as an aluminum wire is arranged parallel to the tube; Japanese Utility Model Provisional Publication No. 62-122801 discloses a pheromone-dispenser having a ring-like shape formed by bending a tube; and Japanese Utility Model Application Publication No. 63-722 discloses a pheromone-dispenser produced by bending a tube.
In the pheromone-dispenser in which a metal wire is arranged parallel to the tube, the tube shows excellent shape-retaining ability since it can easily be bent together with the metal wire. Accordingly, operations for installation such as hooking it on or winding it around a branch or trunk of a plant and the dispenser may stably hold its installed condition, but a problem arises such that the metal wire remains even after the use of the dispenser. The pheromone-dispensers obtained by bending a tube per se or by forming a tube into a ring not only require much expenses for shaping processes, but also the bent tube returns to its original shape, i.e., straight form due to the restoring effect of the plastic if the dispenser is installed over a long time period and it may sometimes fall down from, for instance, the branch on which it is hooked. Moreover, it is difficult to closely arrange a large number of these pheromone-dispensers for packaging and this makes the resulting package bulky and increases the expenses required for packaging and/or circulation.
On the other hand, to dispense with much labor for the installation of these pheromone-dispensers, there has been a need for increasing the amount of the synthetic sex pheromone released per one dispenser and reducing the number of the dispensers to be installed per unit area (installation density). The installation density of the dispenser may be reduced by increasing the capacity of the plastic tube of the pheromone-dispenser and correspondingly increasing the amount of the synthetic liquid pheromone enclosed therein. In this regard, the capacity of the plastic tube can be increased by extending the length of the tube, but such a long length of the tube may interfere with the operations for the installation thereof and may make the packaging and transportation thereof undesirable and quite troublesome. Alternatively, the amount of the liquid pheromone to be enclosed in the plastic tube can be improved by increasing the inner diameter of the plastic tube. However, the rate of diffusion and evaporation of the pheromone should be improved by properly adjusting the wall thickness of the plastic tube in order to ensure a release amount of the pheromone proportional to the amount thereof enclosed. For this reason, the fabrication of the plastic tube becomes difficult, the flexibility of the plastic tube is lowered and this in turn makes the bending thereof and its installation operations difficult.